FDA to Evaluate Drugs Made by Genetically Modified Goats

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FDA to Evaluate Drugs Made by Genetically Modified Goats

For the first time, the FDA will evaluate a drug that comes from a genetically modified animal, a production method that could yield cheap drugs that could be used to treat rare conditions or stockpiled for pandemics and other emergencies.

On Friday the agency will consider a protein-based blood thinner that is produced in the glands of transgenic goats and harvested from their milk. Known as ATryn, the drug is already on the European market, but if approved, it will be the first medication made by a GM animal to be sold in the United States.

"The mammary gland itself has developed naturally to efficiently express a variety of proteins as nutrition for offspring," said ThomasNewberry, the vice president of GTC Biotherapeutics. "Our technology simply provides an extra bit of coding so the mammary gland also makes a protein with human therapeutic value."

GTC Biotherapeutics, based in Framingham, Massachusetts, has mastered the art of making drugs flow from the teats of livestock. Its tricks could slash the price of manufacturing protein-based medications, which are notoriously expensive, allowing drug makers to churn out affordable treatments for exotic diseases.

Doctors use a protein called antithrombin to treat a rare genetic disorder that causes dangerous blood clotting, but that molecule is in very short supply. ATryn contains the same chemical, but it is produced by animals rather than humans.

"As an example, if you were to take all the donated human plasma in the U.S. and devote it to making plasma-derived antithrombin you could get about 100 kg per year," Newberry said. "We can produce 100 kg per year of ATryn from about 150 goats."

Some protein-based drugs can be produced by microbes like yeast, but others require the special touch of mammalian cells. Giant pharmaceutical companies make batches of medication in sophisticated tanks called bioreactors, which are often filled with Chinese hamster ovary cells. But that method is very costly.

By comparison, using goats as living, grass-chewing factories is elegant and inexpensive. Because the drug is only produced in their mammary glands, it doesn't cause health problems for the goats.

"We link the DNA that codes for the human antithrombin protein to a sequence of lactation DNA," Newberry said. "This transgene is then inserted into the single-celled embryo of an animal and the extra gene is only switched on when the animal matures and begins lactating, expressing recombinant antithrombin into its milk and nowhere else in its body."

ATryn has successfully completed human clinical trials, and only needs the green light from the FDA.

At least one more company, PharmAthene is also heading down that road. It has begun human trials of Protexia, a substance that could protect soldiers from chemical weapons. It works by breaking down acetylcholine, the chemical that accumulates and causes seizures when someone inhales nerve gas.